It tells The 200mm F2 has a total of 19 elements, including one Super ED and two ED elements, and the front glass has a fluorine coating
to keep away fingerprints and water.
The editor or writer of Dpreview has no idea of chemistry that F2 is absolutely unsuitable to coat glass ???
Probably they mean fluoride as a metal salt and not elemental F2.
[Edited on 2018-8-13 by metalresearcher]unionised - 13-8-2018 at 11:41
It's over ten years since I was into photography and astronomy so things may have improved,
but from memory, ED lenses ( to make the overall lens system apochromatic) are prone to going cloudy if exposed to moisture.
So if you intend to use the lens for a project then sell it on, good.
If you intend to keep the lens then keep it in a dry atmosphere,
even though the manufacturer claims the unit is sealed.
